Display including emission layer

ABSTRACT

A display capable of preventing an emission layer from deterioration resulting from temperature rise of an electrode also when the same is increased in size and easily connectable with an external current source also when the same is connected with the external current source on a single portion is provided. This display comprises a first electrode formed on a substrate, an emission layer formed on the first electrode, a second electrode formed on the emission layer, a peripheral electrode, arranged to enclose the outer periphery of the second electrode and connected with at least three edges of the outer periphery of the second electrode, having a smaller sheet resistance value than the second electrode, and a current source connection terminal connected to the outer periphery of the peripheral electrode. Thus, current readily flows from the second electrode toward the peripheral electrode, while the current can be dispersedly fed along three or four directions.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a display, and morespecifically, it relates to a display including an emission layer suchas an organic layer.

[0003] 2. Description of the Background Art

[0004] Requirement for flat display devices exhibiting smaller powerconsumption than a generally employed CRT is recently increasedfollowing diversification of information apparatuses. Among such flatdisplay devices, a display employing an organic electroluminescenceelement (hereinafter referred to as an organic EL element) characterizedby high efficiency, thinness/lightweight property and no view angledependency is actively researched and developed.

[0005]FIG. 12 is a perspective view showing the overall structure of aconventional organic EL display. FIG. 13 is a plan view of theconventional organic EL display shown in FIG. 12. Referring to FIGS. 12and 13, anodes 102 of ITO (indium-tin oxide) are formed on a glasssubstrate 101 in the conventional organic EL display. Organic layers 105including hole injection layers, hole transport layers and emissionlayers are formed on the anodes 102. A cathode 103 is formed on theorganic layers 105. This cathode 103 is provided with an outlet terminal104.

[0006] Drive circuits 106 a and 106 b are formed on the glass substrate101. Video signal lines 151 are connected to the drive circuit 106 a.Scanning lines 152 and power supply lines 153 are connected to the drivecircuit 106 b. The outlet terminal 104 of the cathode 103 is connectedto a current supply input terminal 108 for supplying current from acurrent source. The cathode 103 is formed to cover a plurality ofpixels. Therefore, current for driving the plurality of pixelsconcentrically flows into the cathode 103.

[0007] As hereinabove described, the current for driving the pluralityof pixels flows into the cathode 103 in the conventional organic ELdisplay. In this case, the current concentrates to the outlet terminal104 of the cathode 103, disadvantageously leading to resistance heatingof the outlet terminal 104. Particularly when the organic EL display isincreased in size, large current flows to the outlet terminal 104 toincrease resistance heating thereof.

[0008] When resistance heating of the outlet terminal 104 is increased,the temperature of the cathode 103 is increased to disadvantageouslydeteriorate the organic layers 105 located under the cathode 103.

[0009] In general, therefore, various methods are proposed in order tosuppress heat generation in an outlet terminal part. For example,Japanese Patent Laying-Open No. 2001-109398 proposes a structureincreasing the width of an outlet terminal part.

[0010] Even if the width of a single outlet terminal part is increased,however, large current concentrically flows to the single outletterminal part when the display is increased in size, and hence it isdifficult to reduce the quantity of heat generation in the outletterminal part. When the display is increased in size, therefore, it isso difficult to reduce temperature rise of a cathode that it is alsodifficult to prevent organic layers from deterioration resulting fromtemperature rise of the cathode.

[0011] Japanese Patent Laying-Open No. 2001-85158 discloses a techniqueof increasing the width of outlet terminal (drawing terminal) parts of acathode (second electrode) while providing the outlet terminal parts ontwo portions of opposite edges. In general, however, connection with anexternal current source is performed on a single portion and hence it isdifficult to connect the outlet terminals of the cathode (secondelectrode) with the external current source when the outlet terminalsare provided on two portions of the opposite edges. In the structuredisclosed in the aforementioned gazette, further, current can bedispersed to the two outlet terminals (two directions) of the cathode.However, it is difficult to disperse the current in three or fourdirections. When large current flows in a display increased in size,therefore, it is difficult to disperse the current for inhibiting thecathode from heat generation.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide a displaycapable of preventing an emission layer (organic layer) fromdeterioration resulting from temperature rise of an electrode also whenthe display is increased in size and easily connectable with an externalcurrent source also when the display is connected with the externalcurrent source on a single portion.

[0013] Another object of the present invention to inhibit a currentsource connection terminal connected with the external current sourcefrom transferring heat to the electrode in the aforementioned display.

[0014] In order to attain the aforementioned objects, a displayaccording to an aspect of the present invention comprises a firstelectrode formed on a substrate, an emission layer formed on the firstelectrode, a second electrode formed on the emission layer, a peripheralelectrode, arranged to enclose the outer periphery of the secondelectrode and connected with at least three edges of the outer peripheryof the second electrode, having a smaller sheet resistance value thanthe second electrode, and a current source connection terminal connectedto the outer periphery of the peripheral electrode.

[0015] The display according to this aspect is provided with theperipheral electrode, arranged to enclose the outer periphery of thesecond electrode and connected with at least three edges of the outerperiphery of the second electrode, having a smaller sheet resistancevalue than the second electrode as hereinabove described, wherebycurrent readily flows from the second electrode toward the peripheralelectrode and this current can be dispersedly fed in three or fourdirections. Thus, heat generation of the second electrode can be furthersuppressed as compared with a case of dispersedly feeding the currentalong two directions of the second electrode. Consequently, the emissionlayer can be effectively prevented from deterioration resulting fromheat generation (temperature rise) of the second electrode also when thedisplay is increased in size. The current source connection terminal isconnected to the outer periphery of the peripheral electrode arranged toenclose the outer periphery of the second electrode so that the secondelectrode and the single current source connection terminal can beeasily electrically connected with each other through the peripheralelectrode. Consequently, the display can be easily connected with theexternal current source through the single current source connectionterminal also when connected with the external current source on asingle portion. The current source connection terminal is provided onthe outer periphery of the peripheral electrode for increasing thedistance between the current source connection terminal and the secondelectrode by the width of the peripheral electrode, whereby heatgenerated in the current source connection terminal is hardlytransferred to the second electrode. Thus, the second electrode isinhibited from temperature rise, whereby the emission layer can beinhibited from deterioration resulting from temperature rise of thesecond electrode.

[0016] In the display according to the aforementioned aspect, theperipheral electrode may be annularly formed. Further, the peripheralelectrode may be formed to be in contact with the side surface of theouter periphery of the second electrode. The peripheral electrode havinga smaller sheet resistance value than the second electrode preferablycontains at least one of Mg, Ti and Al. When employing such a material,the peripheral electrode having a smaller sheet resistance value thanthe second electrode can be easily formed. Further, only a singlecurrent source connection terminal may be provided.

[0017] In the display according to the aforementioned aspect, theperipheral electrode is preferably connected with three edges of thesecond electrode other than an edge of the second electrodecorresponding to an edge of the peripheral electrode connected with thecurrent source connection terminal, and an opening is preferably formedbetween the edge of the peripheral electrode connected with the currentsource connection terminal and the corresponding edge of the secondelectrode. According to this structure, heat generated in the currentsource connection terminal is further hardly transferred to the secondelectrode, due to the opening. Thus, the emission layer can be furtherinhibited from deterioration resulting from temperature rise of thesecond electrode.

[0018] In the display according to the aforementioned aspect, thecontact area between the second electrode and the peripheral electrodeis preferably increased as receding from the current source connectionterminal. According to this structure, the second electrode can befurther effectively prevented from transfer of heat readily generated inthe current source connection terminal. Thus, the second electrode canbe prevented from temperature rise, whereby the emission layer can beprevented from deterioration resulting from temperature rise of thesecond electrode.

[0019] In this case, an opening is preferably formed in an edge of thesecond electrode closest to the current source connection terminal, twoedges of the second electrode secondly closest to the current sourceconnection terminal are preferably in contact with corresponding edgesof the peripheral electrode through a plurality of outlet terminalsprovided on the two edges of the second electrode, and an edge of thesecond electrode farthest from the current source connection terminal ispreferably totally in contact with a corresponding edge of theperipheral electrode. According to this structure, the second electrodeand the peripheral electrode are in contact with each other on threeedges of the second electrode and corresponding three edges of theperipheral electrode, whereby current dispersedly flows from the secondelectrode toward the peripheral electrode along three directions. Thus,heat generation of the second electrode can be further suppressed ascompared with a case where the current dispersedly flows along twodirections of the second electrode. Thus, the emission layer can beprevented from deterioration resulting from temperature rise of thesecond electrode. In this case, the plurality of outlet terminals may beformed by projecting portions of irregular shapes provided on the twoedges of the second electrode secondly closest to the current sourceconnection terminal.

[0020] In the display according to the aforementioned aspect, theperipheral electrode is preferably formed to be connected with fouredges of the outer periphery of the second electrode. According to thisstructure, current can be uniformly dispersedly fed from the secondelectrode toward the peripheral electrode along four directions. Thus,the quantity of heat generated in the second electrode can be reduced ascompared with a case where the current dispersedly flows along twodirections of the second electrode.

[0021] In the aforementioned structure having the peripheral electrodeconnected with the four edges of the outer periphery of the secondelectrode, the peripheral electrode is preferably formed to be incontact substantially with the overall surfaces of the four edges of theouter periphery of the second electrode. According to this structure,current further readily flows from the second electrode toward theperipheral electrode along four directions, whereby the current can bemore uniformly dispersedly fed. Thus, the quantity of heat generated inthe second electrode can be further reduced as compared with a casewhere the current dispersedly flows along two directions of the secondelectrode.

[0022] In the aforementioned structure having the peripheral electrodeconnected with the four edges of the outer periphery of the secondelectrode, an edge of the second electrode corresponding to an edge ofthe peripheral electrode connected with the current source connectionterminal preferably includes a plurality of outlet terminals, theplurality of outlet terminals are preferably connected to the edge ofthe peripheral electrode connected with the current source connectionterminal, and the peripheral electrode is preferably formed to be incontact substantially with the overall surfaces of remaining three edgesof the second electrode. According to this structure, the secondelectrode and the peripheral electrode are connected with each other onfour edges, whereby current can be dispersedly fed from the secondelectrode to the peripheral electrode along four directions. Thus, heatgeneration of the second electrode can be further suppressed as comparedwith a case where the current is dispersed along two directions of thesecond electrode. Consequently, the emission layer can be effectivelyprevented from deterioration resulting from heat generation (temperaturerise) of the second electrode also when the display is increased insize. The plurality of outlet terminals provided on the edge of thesecond electrode are connected to the edge of the peripheral electrodeconnected with the current source connection terminal so that thecontact area between the plurality of outlet terminals and the edge ofthe peripheral electrode is reduced as compared with a case where oneedge of the second electrode and one edge of the peripheral electrodeare totally in contact with each other, whereby heat generated in thecurrent source connection terminal is further hardly transferred to thesecond electrode. Thus, the second electrode can be inhibited fromtemperature rise, whereby the emission layer can be prevented fromdeterioration resulting from temperature rise of the second electrode.In this case, the plurality of outlet terminals may be formed byprojecting portions of an irregular shape provided on the edge of thesecond electrode corresponding to the edge of the peripheral electrodeconnected with the current source connection terminal.

[0023] In the aforementioned structure having the peripheral electrodeconnected with the four edges of the outer periphery of the secondelectrode, the second electrode preferably includes a plurality ofoutlet terminals formed along four edges of the outer periphery of thesecond electrode, and the peripheral electrode is preferably connectedwith the four edges of the second electrode through the plurality ofoutlet terminals. According to this structure, the second electrode andthe peripheral electrode are connected with each other on four edges,whereby current can be uniformly dispersedly fed from the secondelectrode toward the peripheral electrode along four directions. Thus,heat generation of the second electrode can be further suppressed ascompared with a case where the current dispersedly flows along twodirections of the second electrode. Consequently, the emission layer canbe effectively prevented from deterioration resulting from heatgeneration (temperature rise) of the second electrode also when thedisplay is increased in size. The plurality of outlet terminals providedon the four edges of the second electrode are connected to four edges ofthe peripheral electrode so that the contact areas between the pluralityof outlet terminals and the four edges of the peripheral electrode arereduced as compared with a case of totally brining the four edges of thesecond electrode and the four edges of the peripheral electrode intocontact with each other, whereby heat generated in the current sourceconnection terminal is further hardly transferred to the secondelectrode. Thus, temperature rise of the second electrode can besuppressed, whereby the emission layer can be prevented fromdeterioration resulting from temperature rise of the second electrode.In this case, the plurality of outlet terminals may be formed byprojecting portions of irregular shapes provided on the four edges ofthe peripheral electrode.

[0024] The display according to the aforementioned aspect preferablyfurther comprises cooling means provided in the vicinity of the currentsource connection terminal. According to this structure, the coolingmeans can effectively suppress heat generation of the current sourceconnection terminal readily subjected to concentration of current. Thus,the quantity of heat transferred from the current source connectionterminal to the second electrode through the peripheral electrode can bereduced, whereby the emission layer can be further inhibited fromdeterioration resulting from temperature rise of the second electrode.In this case, the cooling means preferably includes at least one of afan, a cooling fin and a Peltier device. According to this structure,the current source connection terminal readily subjected toconcentration of current can be easily inhibited from heat generation.

[0025] In the display according to the aforementioned aspect, theemission layer preferably includes an organic layer. According to thisstructure, the organic layer can be inhibited from deteriorationresulting from temperature rise of the second electrode in an organic ELelement including the organic layer.

[0026] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a plan view showing the overall structure of an organicEL display according to a first embodiment of the present invention;

[0028]FIG. 2 is a sectional view of the organic EL display according tothe first embodiment taken along the line 100-100 in FIG. 1;

[0029]FIG. 3 is a plan view showing the overall structure of an organicEL display according to a second embodiment of the present invention;

[0030]FIG. 4 is a sectional view of the organic EL display according tothe second embodiment taken along the line 200-200 in FIG. 3;

[0031]FIG. 5 is a sectional view showing cooling means for a currentsupply input terminal of the organic EL display according to the secondembodiment shown in FIG. 3;

[0032]FIG. 6 is a plan view showing the overall structure of an organicEL display according to a third embodiment of the present invention;

[0033]FIG. 7 is a sectional view of the organic EL display according tothe third embodiment taken along the line 300-300 in FIG. 6;

[0034]FIG. 8 is a plan view showing the overall structure of an organicEL display according to a fourth embodiment of the present invention;

[0035]FIG. 9 is a plan view showing the overall structure of an organicEL display according to a fifth embodiment of the present invention;

[0036]FIG. 10 is a sectional view showing a modification of the coolingmeans for the current supply input terminal of the organic EL displayaccording to the second embodiment shown in FIG. 5;

[0037]FIG. 11 is a sectional view showing another modification of thecooling means for the current supply input terminal of the organic ELdisplay according to the second embodiment shown in FIG. 5;

[0038]FIG. 12 is a perspective view showing the overall structure of aconventional organic EL display; and

[0039]FIG. 13 is a plan view showing the overall structure of theconventional organic EL display shown in FIG. 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Embodiments of the present invention are now described withreference to the drawings.

[0041] (First Embodiment)

[0042] Referring to FIGS. 1 and 2, anodes 2 consisting of transparentmetal oxide films of ITO (indium-tin oxide) or the like having athickness of about 100 nm are formed on a glass substrate 1 in anorganic EL display according to a first embodiment of the presentinvention. Organic layers 5 are formed on the anodes 2. The organiclayers 5 consist of hole injection layers formed on the anodes 2, holetransport layers formed on the hole injection layers and emission layersformed on the hole transport layers. A cathode 3 consisting of a lowwork function material such as MgIn having a thickness of about 300 nmis formed on the organic layers 5 to cover the overall structure.

[0043] The glass substrate 1 is an example of the “substrate” accordingto the present invention. The anodes 2 are examples of the “firstelectrode” according to the present invention, and the cathode 3 is anexample of the “second electrode” according to the present invention.The organic layers 5 are examples of the “emission layer” according tothe present invention.

[0044] According to the first embodiment, an annular peripheralelectrode 7 of Mg having a smaller sheet resistance value than thecathode 3 is formed to enclose the outer periphery 3 a of the cathode 3.This annular peripheral electrode 7 is formed to be in contact with theside surfaces of all four edges of the outer periphery 3 a of thecathode 3. The annular peripheral electrode 7 is formed to be in contactwith the upper surface of the glass substrate 1. A current supply inputterminal 8 connected with an external current source is connected to theouter periphery of the peripheral electrode 7. The current supply inputterminal 8 is an example of the “current source connection terminal”according to the present invention.

[0045] Drive circuits 6 a and 6 b are arranged on the glass substrate 1.Video signal lines 51 are connected to the drive circuit 6 a. Scanninglines 52 and power supply lines 53 are connected to the drive circuit 6b. An insulator 9 is embedded between each adjacent pair of pixels, asshown in FIG. 2.

[0046] According to the first embodiment, as hereinabove described, theannular peripheral electrode 7 consisting of the material having asmaller sheet resistance value than the cathode 3 is provided to beconnected with all four edges of the outer periphery 3 a of the cathode3, whereby current readily flows from the cathode 3 toward theperipheral electrode 7 and this current can be uniformly dispersedly fedalong four directions. Thus, heat generation of the cathode 3 can befurther suppressed as compared with a case where the current dispersedlyflows along two directions of the cathode 3. Consequently, the emissionlayers can be effectively prevented from deterioration resulting fromheat generation (temperature rise) of the cathode 3 also when theorganic EL display is increased in size.

[0047] According to the first embodiment, the current supply inputterminal 8 connected with the external current source is provided on theouter periphery of the annular peripheral electrode 7 arranged toenclose the outer periphery 3 a of the cathode 3, whereby the cathode 3can be easily electrically connected with the single current supplyinput terminal 8 through the annular peripheral electrode 7.Consequently, the organic EL display can be easily connected with theexternal current source through the single current supply input terminal8 also when connected with the external current source on a singleportion.

[0048] According to the first embodiment, the current supply inputterminal 8 is provided on the outer periphery of the peripheralelectrode 7 for increasing the distance between the current supply inputterminal 8 and the cathode 3 by the width of the peripheral electrode 7,whereby heat generated in the current supply input terminal 8 readilysubjected to concentration of current is hardly transferred to thecathode 3. Thus, the organic layers 5 can be inhibited fromdeterioration resulting from temperature rise of the cathode 3.

[0049] (Second Embodiment)

[0050] Referring to FIGS. 3 to 5, an opening 20 is provided between anedge of a peripheral electrode 7 connected with a current supplyterminal 8 and a corresponding edge of a cathode 13 in an organic ELdisplay according to a second embodiment of the present invention whilemounting a cooling fin 14 on the current supply terminal 8 in astructure similar to that of the first embodiment shown in FIG. 1. Theremaining structure of the organic EL display according to the secondembodiment is similar to that of the aforementioned organic EL displayaccording to the first embodiment. The organic EL display according tothe second embodiment is now described in detail.

[0051] In the organic EL display according to the second embodiment,anodes 2 of ITO or the like are formed on a glass substrate 1, similarlyto the aforementioned first embodiment. Organic layers 5 consisting ofhole injection layers, hole transport layers and emission layers inascending order are formed on the anodes 2. An insulator 9 is embeddedbetween each adjacent pair of pixel parts.

[0052] The cathode 13 is formed to cover a plurality of pixel parts. Thecathode 13 is an example of the “second electrode” according to thepresent invention. The annular peripheral electrode 7 of a material (Mg)having a lower sheet resistance value than the cathode 13 is formed toenclose the cathode 13. The current supply input terminal 8 is connectedto one edge of the outer periphery of the peripheral electrode 7.

[0053] According to the second embodiment, the opening 20 is formedbetween the edge of the peripheral electrode 7 connected with thecurrent supply input terminal 8 and the corresponding edge of thecathode 13. Side surfaces of three edges of the outer periphery 13 a ofthe cathode 13 and corresponding three edges of the peripheral electrode7 are totally in contact with each other. The peripheral electrode 7 isformed to be in contact with the upper surface of the glass substrate 1.According to the second embodiment, the cooling fin 14 is provided underthe current supply input terminal 8, as shown in FIG. 5. The cooling fin14 is an example of the “cooling means” according to the presentinvention.

[0054] According to the second embodiment, as hereinabove described, theopening 20 is so provided that the cathode 13 can be effectivelyprevented from transfer of heat generated in the current supply inputterminal 8 readily subjected to concentration of current. Thus, thecathode 13 can be prevented from temperature rise, whereby the organiclayers 5 can be inhibited from deterioration resulting from temperaturerise of the cathode 13.

[0055] According to the second embodiment, three edges of the outerperiphery 13 a of the cathode 13 are totally in contact with three edgesof the peripheral electrode 7, whereby current can be dispersedly fedfrom the cathode 13 to the peripheral electrode 7 along threedirections. Thus, heat generation of the cathode 13 can be furthersuppressed as compared with a case where the current dispersedly flowsalong two directions of the cathode 13. Consequently, the organic layers5 can be effectively prevented from deterioration resulting from heatgeneration (temperature rise) of the cathode 13 also when the organic ELdisplay is increased in size.

[0056] According to the second embodiment, further, the cooling fin 14is provided under the current supply input terminal 8, whereby heatgeneration of the current supply input terminal 8 readily subjected toconcentration of current can be effectively suppressed. Consequently,the quantity of heat transferred from the current supply input terminal8 to the cathode 13 through the peripheral electrode 7 can be reduced.Thus, the organic layers 5 can be further inhibited from deteriorationresulting from temperature rise of the cathode 13.

[0057] According to the second embodiment, in addition, the currentsupply input terminal 8 connected with the external current source isprovided on the outer periphery of the annular peripheral electrode 7arranged to enclose the outer periphery 13 a of the cathode 13, wherebythe cathode 13 can be easily electrically connected with the singlecurrent supply input terminal 8 through the annular peripheral electrode7. Consequently, the organic EL display can be easily connected with theexternal current source through the single current supply input terminal8 also when connected with the external current source on a singleportion.

[0058] (Third Embodiment)

[0059] Referring to FIGS. 6 and 7, a cathode 23 and a peripheralelectrode 7 are totally in contact with each other on three edges of thecathode 23 while one edge of the cathode 23 is connected to theperipheral electrode 7 through a plurality of outlet terminals 23 b inan organic EL display according to a third embodiment of the presentinvention. The remaining structure of the organic EL display accordingto the third embodiment is similar to that of the aforementioned organicEL display according to the first embodiment.

[0060] According to the third embodiment, an edge of the cathode 23corresponding to an edge of the peripheral electrode 7 connected with acurrent supply input terminal 8 is irregularly formed for forming theplurality of outlet terminals 23 b by projecting portions of theirregular shape. The edge of the peripheral electrode 7 connected withthe current supply input terminal 8 is connected with one edge of thecathode 23 through the plurality of outlet terminals 23 b. The remainingthree edges of the outer periphery 23 a of the cathode 23 are formed tobe totally in contact with the peripheral electrode 7. The cathode 23 isan example of the “second electrode” according to the present invention.

[0061] According to the third embodiment, as hereinabove described, theperipheral electrode 7 and the cathode 23 are connected with each otherthrough the overall surfaces of the three edges of the cathode 23 andthe plurality of outlet terminals 23 b provided on the remaining edge,whereby current flowing to the cathode 23 can be substantially uniformlyfed along four directions. Thus, heat generation of the cathode 23 canbe further suppressed as compared with a case where the currentdispersedly flows along two directions of the cathode 23. Consequently,emission layers can be effectively prevented from deteriorationresulting from heat generation (temperature rise) of the cathode 23 alsowhen the organic EL display is increased in size.

[0062] According to the third embodiment, the edge of the peripheralelectrode 7 connected with the current supply input terminal 8 and thecorresponding edge of the cathode 23 are connected with each otherthrough the plurality of outlet terminals 23 b, whereby the contact areacan be reduced as compared with a case of totally bringing the cathode23 and the peripheral electrode 7 into contact with each other. Thus,the quantity of heat generated in the current supply input terminal 8readily subjected to concentration of current and transferred to thecathode 23 can be reduced. Thus, organic layers 5 can be effectivelyprevented from deterioration resulting from temperature rise of thecathode 23.

[0063] According to the third embodiment, further, the current supplyinput terminal 8 connected with the external current source is providedon the outer periphery of the annular peripheral electrode 7 arranged toenclose the outer periphery of the cathode 23, whereby the cathode 23can be easily electrically connected with the single current supplyinput terminal 8 through the annular peripheral electrode 7.Consequently, the organic EL display can be easily connected with theexternal current source through the single current supply input terminal8 also when connected with the external current source on a singleportion.

[0064] (Fourth Embodiment)

[0065] Referring to FIG. 8, an opening 40 is provided between an edge ofa peripheral electrode 7 connected with a current supply input terminal8 and a corresponding edge 33 c of a cathode 33 while other two edges ofthe cathode 33 are connected to the peripheral electrode 7 through aplurality of outlet terminals 33 b and the remaining edge 33 a of thecathode 33 is totally brought into contact with the peripheral electrode7 in an organic EL display according to a fourth embodiment of thepresent invention. The remaining structure of the organic EL displayaccording to the fourth embodiment is similar to that of the organic ELdisplay according to the first embodiment. The organic EL displayaccording to the fourth embodiment is now described in detail.

[0066] In the organic EL display according to the fourth embodiment, theopening 40 is provided between the edge of the peripheral electrode 7connected with the current supply input terminal 8 and the correspondingedge 33 c of the cathode 33. The plurality of outlet terminals 33 bconsisting of projecting portions of irregular shapes are formed onother two edges of the cathode 33 at prescribed intervals. These twoedges of the cathode 33 and two edges of the peripheral electrode 7 areconnected with each other through the plurality of outlet terminals 33b. The remaining edge 33 a of the cathode 33 is totally brought intocontact with the remaining edge of the peripheral electrode 7. Thecathode 33 is an example of the “second electrode” according to thepresent invention.

[0067] According to the fourth embodiment, as hereinabove described, thecontact area between the cathode 33 and the peripheral electrode 7 isincreased as receding from the current supply input terminal 8. In otherwords, the opening 40 is formed on the edge 33 c of the cathode 33closest the current supply input terminal 8 while the two edges of thecathode 33 secondly closest thereto are connected with the peripheralelectrode 7 through the plurality of outlet terminals 33 b, and the edge33 a of the cathode 33 farthest from the current supply input terminal 8is totally brought into contact with the corresponding edge of theperipheral electrode 7.

[0068] According to the fourth embodiment, as hereinabove described, thecontact area between the cathode 33 and the peripheral electrode 7 isincreased as receding from the current supply input terminal 8, wherebythe cathode 33 can be further effectively prevented from transfer ofheat readily generated in the current supply input terminal 8. Thus, thecathode 33 can be prevented from temperature rise, whereby organiclayers 5 can be prevented from deterioration resulting from temperaturerise of the cathode 33.

[0069] According to the fourth embodiment, further, the cathode 33 andthe peripheral electrode 7 are in contact with each other on three edgesof the cathode 33 and the corresponding three edges of the peripheralelectrode 7, whereby current dispersedly flows from the cathode 33toward the peripheral electrode 7 along three directions. Therefore,heat generation of the cathode 33 can be further suppressed as comparedwith a case where the current dispersedly flows along two directions ofthe cathode 33. Thus, emission layers can be prevented fromdeterioration resulting from temperature rise of the cathode 33.

[0070] According to the fourth embodiment, in addition, the currentsupply input terminal 8 connected with the external current source isprovided on the outer periphery of the annular peripheral electrode 7arranged to enclose the outer periphery of the cathode 33, whereby thecathode 33 can be easily electrically connected with the single currentsupply input terminal 8 through the annular peripheral electrode 7.Consequently, the organic EL display can be easily connected with theexternal current source through the single current supply input terminal8 also when connected with the external current source on a singleportion.

[0071] (Fifth Embodiment)

[0072] Referring to FIG. 9, a plurality of outlet terminals 43 a areformed on all of four edges of a cathode 43 at prescribed intervals forconnecting four edges of the cathode 43 with corresponding four edges ofa peripheral electrode 7 through the outlet terminals 43 a in an organicEL display according to a fifth embodiment of the present invention. Theremaining structure of the organic EL display according to the fifthembodiment is similar to that of the organic EL display according to thefirst embodiment.

[0073] According to the fifth embodiment, the plurality of outletterminals 43 a consisting of projecting portions of irregular shapes areprovided at prescribed intervals along four edges of the cathode 43.Four edges of the cathode 43 are connected with the corresponding fouredges of the peripheral electrode 7 through the plurality of outletterminals 43 a. The cathode 43 is an example of the “second electrode”according to the present invention.

[0074] According to the fifth embodiment, as hereinabove described, fouredges of the cathode 43 are connected with the corresponding four edgesof the peripheral electrode 7 through the plurality of outlet terminals43 a, whereby current flowing from the cathode 43 toward the peripheralelectrode 7 can be uniformly dispersed along four directions. Thus, heatgeneration of the cathode 43 can be further suppressed as compared witha case where the current dispersedly flows along two directions of thecathode 43. Consequently, emission layers can be effectively preventedfrom deterioration resulting from heat generation (temperature rise) ofthe cathode 43 also when the organic EL display is increased in size.

[0075] According to the fifth embodiment, the cathode 43 and theperipheral electrode 7 are connected with each other through theplurality of outlet terminals 43 a so that the contact area between thecathode 43 and the peripheral electrode 7 can be reduced as comparedwith a case of totally bringing the cathode 43 and the peripheralelectrode 7 into contact with each other. When a current supply inputterminal 8 generates heat, therefore, the heat can be rendered hardlytransferable to the cathode 43. Thus, the cathode 43 can be preventedfrom temperature rise. Therefore, organic layers 5 can be effectivelyprevented from deterioration resulting from temperature rise of thecathode 43.

[0076] According to the fifth embodiment, the current supply inputterminal 8 connected with an external current source is provided on theouter periphery of the annular peripheral electrode 7 arranged toenclose the outer periphery of the cathode 43 so that the cathode 43 canbe easily electrically connected with the single current supply inputterminal 8 through the annular peripheral electrode 7. Consequently, theorganic EL display can be easily connected with the external currentsource through the single current supply input terminal 8 also whenconnected with the external current source on a single portion.

[0077] Although the present invention has been described and illustratedin detail, it is clearly understood that the same is by way ofillustration and example only and is not to be taken by way oflimitation, the spirit and scope of the present invention being limitedonly by the terms of the appended claims.

[0078] While the display according to the present invention is appliedto an organic EL display in each of the aforementioned embodiments, forexample, the present invention is not restricted to this but is alsoapplicable to a display, other than the organic EL display, includingemission layers.

[0079] While the peripheral electrode 7 is made of Mg in each of theaforementioned embodiments, the present invention is not restricted tothis but another material may alternatively be employed so far as thesheet resistance value thereof is smaller than that of the cathode. Forexample, Ti or Al is conceivably employable as the material for theperipheral electrode 7. Alternatively, a binary alloy or a ternary alloyof Al—Ti, Al—Cr, Al—Mo, Al—W, Al—Ta, Al—Cu or Al—Nd may be employed.

[0080] While the anodes are arranged under the organic layers and thecathode is arranged on the organic layers in each of the aforementionedembodiments, the present invention is not restricted to this but theanodes may alternatively be arranged on the organic layers and thecathode may alternatively be arranged under the organic layers.

[0081] While the cooling fin 14 is employed in the aforementioned secondembodiment as the cooling means for the current supply input terminal 8,the present invention is not restricted to this but another coolingmeans may alternatively be employed. For example, a fan 15 may beprovided under a current supply input terminal 8 as shown in FIG. 10, ora Peltier device 16 may be provided as a cooling element under a currentsupply input terminal 8 as shown in FIG. 11. According to thisstructure, the current supply input terminal 8 readily generating heatdue to concentration of current can be easily cooled, whereby thequantity of heat transferred from the power supply input terminal 8 tothe cathode 13 through the peripheral electrode 7 can be reduced.Consequently, the organic layers 5 can be further inhibited fromdeterioration resulting from temperature rise of the cathode 13.

What is claimed is:
 1. A display comprising: a first electrode formed ona substrate; an emission layer formed on said first electrode; a secondelectrode formed on said emission layer; a peripheral electrode,arranged to enclose the outer periphery of said second electrode andconnected with at least three edges of the outer periphery of saidsecond electrode, having a smaller sheet resistance value than saidsecond electrode; and a current source connection terminal connected tothe outer periphery of said peripheral electrode.
 2. The displayaccording to claim 1, wherein said peripheral electrode is annularlyformed.
 3. The display according to claim 1, wherein said peripheralelectrode is formed to be in contact with the side surface of the outerperiphery of said second electrode.
 4. The display according to claim 1,wherein said peripheral electrode having a smaller sheet resistancevalue than said second electrode contains at least one of Mg, Ti and Al.5. The display according to claim 1, wherein only one said currentsource connection terminal is provided.
 6. The display according toclaim 1, wherein said peripheral electrode is connected with three edgesof said second electrode other than an edge of said second electrodecorresponding to an edge of said peripheral electrode connected withsaid current source connection terminal, and an opening is formedbetween said edge of said peripheral electrode connected with saidcurrent source connection terminal and said corresponding edge of saidsecond electrode.
 7. The display according to claim 1, wherein thecontact area between said second electrode and said peripheral electrodeis increased as receding from said current source connection terminal.8. The display according to claim 7, wherein an opening is formed in anedge of said second electrode closest to said current source connectionterminal, two edges of said second electrode secondly closest to saidcurrent source connection terminal are in contact with correspondingedges of said peripheral electrode through a plurality of outletterminals provided on said two edges of said second electrode, and anedge of said second electrode farthest from said current sourceconnection terminal is totally in contact with a corresponding edge ofsaid peripheral electrode.
 9. The display according to claim 8, whereinsaid plurality of outlet terminals are formed by projecting portions ofirregular shapes provided on said two edges of said second electrodesecondly closest to said current source connection terminal.
 10. Thedisplay according to claim 1, wherein said peripheral electrode isformed to be connected with four edges of the outer periphery of saidsecond electrode.
 11. The display according to claim 10, wherein saidperipheral electrode is formed to be in contact substantially with theoverall surfaces of said four edges of the outer periphery of saidsecond electrode.
 12. The display according to claim 10, wherein an edgeof said second electrode corresponding to an edge of said peripheralelectrode connected with said current source connection terminalincludes a plurality of outlet terminals, said plurality of outletterminals are connected to said edge of said peripheral electrodeconnected with said current source connection terminal, and saidperipheral electrode is formed to be in contact substantially with theoverall surfaces of remaining three edges of said second electrode. 13.The display according to claim 12, wherein said plurality of outletterminals are formed by projecting portions of an irregular shapeprovided on said edge of said second electrode corresponding to saidedge of said peripheral electrode connected with said current sourceconnection terminal.
 14. The display according to claim 10, wherein saidsecond electrode includes a plurality of outlet terminals formed alongfour edges of the outer periphery of said second electrode, and saidperipheral electrode is connected with said four edges of said secondelectrode through said plurality of outlet terminals.
 15. The displayaccording to claim 14, wherein said plurality of outlet terminals areformed by projecting portions of irregular shapes provided on said fouredges of said peripheral electrode.
 16. The display according to claim1, further comprising cooling means provided in the vicinity of saidcurrent source connection terminal.
 17. The display according to claim16, wherein said cooling means includes at least one of a fan, a coolingfin and a Peltier device.
 18. The display according to claim 1, whereinsaid emission layer includes an organic layer.